ADRENOCORTICAL AND ADRENOMEDULLARY HOMOLOGS IN 8 SPECIES OF ADULT ANDDEVELOPING TELEOSTS - MORPHOLOGY, HISTOLOGY, AND IMMUNOHISTOCHEMISTRY

Morphology, histology, and immunohistochemistry of the adrenocortical and adrenomedullary homologs (adrenal glands) of the following develop ing and adult teleosts were examined: Salmoniformes-Oncorhynchus mykis s (rainbow trout), Salmo trutta fario (brown trout), Coregonus lavaret us (white fish); Cyprinodontiformes-Gambusia affinis (mosquito fish). Perciformes-Dicentrarchus labrax (sea bass), Sparus aurata (sea bream) , Diplodus sargus (white bream), Oblada melanura (saddled bream). The anatomical relationships of the gland with the renal system and venous vessels were also noted. in adults of all species steroidogenic and c atecholaminergic chromaffin cells were found in the head kidney, which is pronephric in origin and subsequently transformed into a hematopoi etic lymphatic organ. In Perciformes, chromaffin cells are distributed around the anterior and posterior cardinal veins and ducts of Cuvier; in Salmoniformes, around the posterior cardinal veins and in the hema topoietic tissue; and in G. affinis, around the ducts of Cuvier and po sterior cardinal veins, while a few are visible also around the sinus venosus. in Perciformes and Salmoniformes, numerous chromaffin cells a re also present in the posterior kidney, derived from the opisthonephr os, in contact with the caudal vein. Steroidogenic cells are always co nfined to the head kidney. During development chromaffin and steroidog enic cells appear early after hatching in the pronephric kidney, at th e level of the ducts of Cuvier and of the cephalic part of the posteri or cardinal veins. Later, chromaffin cells in Perciformes reach the an terior cardinal veins, and subsequently, in both Perciformes and Salmo niformes, they reach the developing posterior kidney. Their localizati on along the posterior kidney is still in progress about 4 months afte r hatching and is completed about a year after hatching. These finding s support the concept that the structure of the adrenal gland in teleo sts is intermediate between that of the other actinopterygians and tha t of tetrapods. The development differs from that of tetrapods in that it occurs mainly in the pronephros and only later do chromaffin cells reach the opisthonephric kidney. (C) 1997 Academic Press.